In an image display device provided with a backlight, such as a liquid crystal display device, by controlling the luminance of the backlight based on an input image, it is possible to suppress power consumption of the backlight and improve the image quality of a display image. In particular, by dividing a screen into a plurality of areas and controlling the luminance of a backlight light source corresponding to an area based on an input image in the area, it is possible to achieve lower power consumption and higher image quality. Hereinafter, a method that drives a display panel while controlling the luminance of a backlight light source based on an input image in an area in this manner will be referred to as “area active driving”.
In an image display device that performs area active driving, as a backlight light source, for example, RGB light emitting diodes (LEDs), a white LED, or the like is used. The luminance of LEDs corresponding to each area (the luminance at the time of light emission) is determined based on a maximum value, an average value, or the like of the luminance of pixels in each area and is provided to a driving circuit for a backlight as LED data. Moreover, data for display (in a liquid crystal display device, data for controlling the light transmittance of a liquid crystal) is generated based on the LED data and an input image, and the data for display is provided to a driving circuit for a display panel. In the case of the liquid crystal display device, the luminance of each pixel on the screen is the product of the luminance of light from the backlight and the light transmittance based on the data for display.
Incidentally, the light emitted from the LEDs in a certain area illuminates not only the area, but also surrounding areas. In other words, a certain area is illuminated with not only the light emitted from the LEDs of the area, but also the light emitted from the LEDs of the surrounding areas. Thus, the luminance displayed in each area has to be calculated in consideration of diffusion (spreading) of the light emitted from each LED.
For this reason, in the past, there has been a method for avoiding a failure of an output image by correcting data for display by generating a correction table by measuring the actual luminance distribution. For example, in PTL 1, calculating the light transmittance of a display element based on an input image and the display luminance corrected in consideration of diffusion from the LED data for each area is described. Moreover, in PTL 2, calculating the light transmittance by correcting an input image in order to eliminate the unevenness of the luminance of adjacent areas in area active driving is described.